Stem cells generally refer to undifferentiated cells before differentiation, which can be obtained from various tissues. Stem cells have properties capable of continuously producing cells identical to themselves for a certain amount of time in an undifferentiated state, and also have properties capable of differentiating into various types of cells, which constitute biological tissues, under proper conditions.
Stem cells can be broadly classified into embryonic stem cells and adult stem cells, according to their differentiation potential and creation time. In addition, stem cells can be classified according to their differentiation potential into pluripotent, multipotent, and unipotent stem cells.
Adult stem cells can be classified as multipotent or unipotent stem cells. Representative adult stem cells include mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs). It is known that mesenchymal stem cells differentiate into chondrocytes, osteoblasts, adipocytes, myocytes, and neurons, and that hematopoietic stem cells mainly differentiate into blood cells in blood, such as erythrocytes, leukocytes, or platelets.
Meanwhile, pluripotent stem cells refer to stem cells having multipotency to differentiate into all three germ layers constituting the body, and thus are capable of differentiating into every cell or organ tissue of the human body. Generally, embryonic stem cells fall into this category. Human embryonic stem cells raise many ethical concerns, because they are created from embryos that may develop into human beings. However, embryonic stem cells are known as having an excellent ability to proliferate and differentiate, compared to adult stem cells. Adult stem cells cause less ethical issues, because they can be obtained from bone marrow, blood, brain, skin, and the like. However, adult stem cells have a limited ability to differentiate, compared to embryonic stem cells.
As a solution to overcome these problems, various techniques have been attempted to dedifferentiate cells derived from adult stem cells to thereby produce customized pluripotent stem cells similar to embryonic stem cells. Representative techniques include fusion with ES cells, somatic cell nuclear transfer, reprogramming by gene factor, and the like. According to fusion with ES cell, induced cells further have two pairs of genes, and this causes a problem in terms of stability of cells. Somatic cell nuclear transfer has problems in that it requires a large number of eggs and has very low efficiency. Reprogramming by gene factor is a technique of using viruses containing oncogenes to insert specific genes to thereby induce dedifferentiation, and this technique poses a high risk of cancer occurrence and is disadvantageous in terms of possibility of development of cell therapy products due to low efficiency and difficulty in terms of methods.
In order to obtain pluripotent stem cells successfully and abundantly, medium compositions in the stage of culturing isolated umbilical cord mononuclear cells are very important. Thus, studies are required to produce an increased amount of pluripotent stem cells by a highly efficient induction method.
The matters provided in the above background art are only intended to help better understand the background of the present invention. It should not be understood, however, that these matters fall within the prior art already known to a person having ordinary knowledge in the art.